Public opinion toward foreign adversaries shapes and constrains diplomatic options. Prior research has largely relied on sentiment analysis and survey based measures, providing limited insight into how sustained narrative changes (beyond transient emotional reactions) might follow diplomatic engagement. This study examines the extent to which high stakes diplomatic summits shape how adversaries are framed in online discourse. We analyze U.S.-North Korea summit diplomacy (2018-2019) using a Difference-in-Difference(DiD) design on Reddit discussions. Using multiple control groups (China, Iran, Russia) to adjust for concurrent geopolitical shocks, we integrate a validated Codebook LLM framework for framing classification with graph based discourse network analysis that examines both edge level relationships and community level narrative structures. Our results reveal short term asymmetric persistence in framing responses to diplomacy. While both post level and comment level sentiment proved transient (improving during the Singapore Summit but fully reverting after the Hanoi failure),framing exhibited significant stability: the shift from threat oriented to diplomacy oriented framing was only partially reversed. Structurally, the proportion of threat oriented edges decreased substantially (48% -> 28%) while diplomacy oriented structures expanded, and these shifts resisted complete reversion after diplomatic failure. These findings suggest that diplomatic success can leave a short-term but lasting imprint on how adversaries are framed in online discourse, even when subsequent negotiations fail.

翻译：公众对外国对手的看法塑造并制约着外交选项。先前研究主要依赖情感分析和基于调查的测量方法，对持续叙事变化（超越短暂情绪反应）如何随外交接触而变化提供了有限见解。本研究探讨高风险外交峰会在多大程度上塑造了在线话语中对对手的框架化方式。我们采用双重差分法设计分析Reddit上关于美朝峰会外交（2018-2019年）的讨论。通过使用多个对照组（中国、伊朗、俄罗斯）来调整同时发生的地缘政治冲击，我们将经过验证的Codebook LLM框架分类方法与基于图的话语网络分析相结合，同时考察边级关系和社区级叙事结构。我们的研究结果揭示了框架对外交响应的短期非对称持续性。虽然帖子和评论层面的情感被证明是短暂的（在新加坡峰会期间改善但在河内失败后完全逆转），但框架表现出显著稳定性：从威胁导向到外交导向的框架转变仅部分逆转。在结构上，威胁导向边的比例大幅下降（48%→28%），而外交导向结构得到扩展，且这些转变在外交失败后抵抗了完全逆转。这些发现表明，即使后续谈判失败，外交成功仍能在在线话语中对对手的框架化方式留下短期但持久的印记。